Spray a slow cooker with nonstick cooking spray. Place chicken in the bottom of slow cooker and season with salt and pepper.
In a small bowl, whisk together chili powder, garlic powder, onion powder and oregano then sprinkle on top of chicken.
Pour undrained can of Rotel on top of chicken. Cover and cook on low for 4-6 hours or high for 2-3.
When chicken is done cooking, remove from slow cooker and let rest on a cutting board for 5 minutes then shred in a bowl or stand mixer. Add some juice from the slow cooker to the shredded chicken, if desired.
Preheat oven to 400 degrees F.
Divide shredded chicken between tortillas and top with shredded cheese. Fold in opposite sides of each tortilla and roll up.
Place seam-side down on a baking sheet sprayed with nonstick cooking spray. Brush melted butter on top of each chimichanga.
Bake for 25 minutes or until golden brown on top. Garnish with desired toppings